1. Field of the Invention
The present invention relates to an α-SiAlON to be utilized as a phosphor, and a light-emitting device, an illumination device, a signal device, a liquid crystal panel and an image display device utilizing the same.
2. Description of the Related Art
α-SiAlONs activated by a particular rare-earth element, as nitride or oxynitride phosphors, have been known to have useful fluorescence characteristics, and have been applied to a white LED and the like. α-SiAlONs have such a construction that Si—N bonds of an α-silicon nitride crystal are partially substituted with Al—N bonds and an Al—O bonds, and particular elements (Ca, and Li, Mg, Y or a lanthanide metal except for La and Ce) penetrate into a crystal lattice in the form of solid solutions in order to maintain electric neutrality. A rare-earth element serving as a luminescent center is used as a part of the elements penetrating in the form of solid solutions to thereby exert fluorescence characteristics. Among them, an α-SiAlON phosphor in which Ca is present in the form of a solid solution and a part thereof is substituted with Eu is excited at a relatively good efficiency in a wide wavelength region of ultraviolet to blue to emit yellow to orange light. As an attempt for further improving fluorescence characteristics of such an α-SiAlON, for example, selecting of an α-SiAlON having a particular average particle diameter by a classification treatment has been proposed (Patent Document 1).